Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

A Catalogue of Radio AGN behind the LMC (#223)

Gregory Goldstein 1 , Miroslav Filipovic , Nicholas Tothill , Evan Crawford
  1. Univ Western Sydney, Greenwich, NSW, Australia

We have prepared a catalogue of 230 known and recently identified radio AGN in a defined 7 x 7 degree area (the field of the Spitzer SAGE survey, described in Meixner et al (2006)) behind the LMC using multiwavelength studies.

Identification of new AGN behind the LMC and other nearby galaxies remains important in several areas of research. Over the last 6 years over 7000 AGN candidates have been detected behind the LMC, in particular using microlensing studies such as MACHO and OGLE, and the Spitzer SAGE IR.

Radio AGN were detected as LMC background sources in ATCA and MOST radio images; by mid-IR spectrum using criteria of Stern et al (2005); by optical variability  (MACHO, OGLE); in catalogues/published studies as AGN/quasars with spectroscopic redshifts; and with X-ray counterparts.

A total of 230 AGN candidates were included in the catalogue. Candidates were identified as AGN in at least two of the above categories. Radio AGN were classified as point or extended based on appearance, the major axis size, and the ratio of peak/integrated flux density at 36, 20, 6, and 3 cm wavelengths. There were 124 point, 80 extended, and 26 paired sources; 35 AGN had flat radio spectum, 145 steep and 45 ultra steep; 159 had a AGN IR spectrum, 64 had X-ray counterpart, 25 had a redshift.

The angular separations of the radio source and the optical/IR/xray sources have been measured. As expected by the AGN unification theory, flat spectrum radio AGN have a smaller separation of the radio-optical/IR sources than steep spectrum.

15 of the 124 radio AGN that were point sources (12.0%) met criteria for “faint infrared radio sources”. 

A detailed catalogue of radio AGN is being published online. The catalogue will in addition provide a list of 181 confirmed AGN (with spectroscopic redshifts) in the study area that do NOT have radio counterparts. Thus of a total (181+25) 206 AGN with redshifts in the area, 12.1% have radio counterparts.

  1. Stern et al, The Astrophysical Journal, 631:163–168, 2005 September 20
  2. Meixner et al The Astronomical Journal, 132:2268–2288, 2006 December